The overall objective of this project is to elucidate the mechanisms by which FSH and calcium regulate the Sertoli cell of the mammalian testis and thus provide a link between hormonal modulation of genetic information and the physiological functions of the target cell. In this manner it is hoped to gain some insight into the problem of the control and regulation of the male reproductive process. FSH regulates the synthesis of protein kinase inhibitor (PKI) and calcium redistribution in the Sertoli cell. Calcium action requires the binding protein calmodulin. Our approach to the problem is to use PKI to assess events that require cyclic nucleotide-mediated protein phosphorylation and calmodulin to assess processes under control by changes in calcium levels. Immunological, ultrastructural and biochemical approaches are used to elucidate the intracellular distribution and functions of PKI and calmodulin in the Sertoli cells. In addition, regulation of sperm motility by calcium and cyclic AMP is under investigation. Similar approaches are being undertaken to describe the regulation of microtubules and microfilaments in developing germ cells and spermatozoa. Finally, experiments will be carried out to investigate how two enzymes, myosin light chain kinase and phosphorylase b kinase, are regulated by Ca ions - and cAMP-dependent phosphorylation. These enzymes are involved in controlling stimulus-secretion coupling in testicular cells. Our studies should provide a firm base by which to understand the interaction of calcium and cAMP in the regulation of the male reproductive system.